1. Field of the Invention
The present invention relates to a sheet material guiding mechanism capable of reliably guiding a sheet material to be fed. The invention also relates to a sheet material feeding and conveying device provided with such mechanism, as well as a recording apparatus, such as a printer, and facsimile equipment.
2. Related Background Art
Conventionally, a recording apparatus, such as a printer, a copying machine, and facsimile equipment, has used a post card, an envelope, and other thick paper sheets, and a thin plastic sheet and other special sheet materials, in addition to a plain paper sheet. The supply of sheet material has been performed one by one by manual insertion or by an automatic and continuous feeding by means of a sheet material feeding and conveying device. Then, for the execution of feeding and conveying operations, it is necessary to regulate the sheet material so as to feed it without skew. In the feeding portion, therefore, it is arranged to regulate both sides of sheet material by placing them along the guides when sheet material is stacked.
Usually, the reference of sheet material is established on one side. Therefore, the structure is arranged to fix the guide on the reference side, and make the guide on non-reference side movable. In the movable-guide structure of the kind, the movable guide pinches one side of the pressure plate, which enables the stacked sheet material to be biased to the feed roller, and then, the movable guide is made slidable on the pressure plate, thus fixing it in the predetermined position. As the structure for fixing the movable guide, the following is in practice, for example:
(1) A movable guide pinches a pressure plate, and the force of fixation for the movable guide is output only by the mold elasticity and friction coefficient thereof.
(2) An elastic member and a friction member are inserted between the movable guide and the pressure plate in order to output the force of fixation for the movable guide.
(3) The knurled portion is arranged for the pressure plate, and the engaging portion is provided for the movable guide corresponding to the knurled portion of the movable guide so as to enable it to be fixed in a position matching the size of a sheet material to be used. When the movable guide should move in accordance with the size of sheet material to be used, the operator nips the operating section of the movable guide. Then, the aforesaid engaging portion is released from the knurled portion to allow the movable guide to move.
However, the following problems are encountered in the conventional examples described above:
(1) It is difficult to set the optimum operating force with the structure in which the movable guide pinches the pressure plate to output the force of fixation for the movable guide only by the mold elasticity and friction coefficient thereof. In some case, the operating force is lowered due to such phenomenon as creeping or the like.
(2) The structure having the elastic member and friction member inserted between the movable guide and pressure plate makes it possible to provide the countermeasure needed for the set up of the operating force and the problem of creeping.
However, there is still a problem of increased costs, and the inferior operability when the force of fixation should increase in order to suppress the skew of a sheet material having a firmness that requires a stronger operating force.
(3) The locking mechanism that uses the knurled portion overcomes the aforesaid problems, but the operator is required to nip the operating section. Then, there is still a problem to be solved before realizing the operation that may be carried out by use of one finger, which is needed for eliminating the existing disability.